support \e in \file and \filenq; this is useful for Windows paths

Doc/texinputs/python.sty

@@ -849,7 +849,7 @@
 \newcommand{\strong}[1]{{\bf #1}}
 % let's experiment with a new font:
 \newcommand{\file}[1]{`\filenq{#1}'}
-\newcommand{\filenq}[1]{{\py@smallsize\textsf{#1}}}
+\newcommand{\filenq}[1]{{\py@smallsize\textsf{\let\e=\textbackslash#1}}}
 
 % Use this def/redef approach for \url{} since hyperref defined this already,
 % but only if we actually used hyperref: